1. Field of the Invention
The present invention relates to an inspecting apparatus for electrically inspecting an object such as a semiconductor wafer, particularly, to an inspecting apparatus into which air is blown for improving the cleanliness.
2. Description of the Related Art
The conventional inspecting apparatus comprises in general a housing section for housing an object such as semiconductor wafers transferred in units of cassettes, a transfer mechanism arranged rearward of the housing section having forks or arms for transferring the object within the cassette, a table for receiving the object transferred by the transfer mechanism, and an electrical inspecting mechanism constructed by, for example, a probe card and a tester, said probe card serving to bring contactors such as probes into contact with the object on the table for electrical inspection of the object. For performing an electrical inspection, the object is taken out of the cassette by the fork for prealignment, followed by transferring the object onto the table by using the fork. Then, the table is moved in X-, Y- and .theta.-directions for locating the object in an inspecting position. Further, the table is over-driven in a Z-direction so as to bring the object into contact with the contactors. As a result, the object is allowed to receive a signal emitted from the tester for a predetermined electrical inspection.
It was customary in the past to use the inspecting apparatus for an electrical inspection of an integrated circuit formed in the preliminary steps such as a film-forming step and an etching step. Therefore, particles are less likely to offer problems during the inspection than in the preliminary steps. Nevertheless, it is desirable to apply an electrical inspection to the object under a particle-free environment in which particle generation is suppressed substantially completely. However, the presence of a transfer mechanism, driving mechanism of a table, etc. within the inspecting apparatus makes it unavoidable for particles such as dust to be generated, though the particle generation is very small. An inspecting apparatus which is intended to overcome this difficulty is proposed in each of, for example, Japanese Patent Disclosure (Kokai) No. 63-151036, Japanese Patent Disclosure No. 4-24935, Japanese Patent Disclosure No. 5-36766, and Japanese Patent Disclosure No. 5-41418. Specifically, the inspecting apparatus proposed in these publications comprises an exhaust fan or the like to cause the air within the apparatus body to flow downward so as to discharge the particles to the outside and to prevent heat accumulation within the apparatus body.
As described above, the inspecting apparatus is used generally for applying an electrical inspection to an object having an integrated circuit formed on the surface thereof. However, there are inspecting apparatuses which are used in a special fashion. For example, objects processed in preliminary steps are sampled and, then, inspected in some cases including an initial operation of a newly constructed plant for manufacturing semiconductor devices in order to inspect whether the apparatus used in each preliminary step performs its function as desired before full operation of the semiconductor manufacturing plant. In such a case, the object after inspection performed by using the inspecting apparatus must be brought back to the preceding step for the subsequent processings. It follows that, if particles are attached to the object brought back to the preceding step, it is impossible to evaluate accurately the subsequent process steps. Naturally, it is necessary to take special measures against particles when it comes to the inspecting apparatus used in a special fashion. To meet this requirement, proposed is an inspecting apparatus which is constructed such that a down stream of air is formed within the apparatus body so as to prevent the particles within the apparatus body from being attached to the object. Incidentally, the term "particles" noted above denotes the floating particles such as dust, which are generated from rubbish, metals, organic materials and human body.
However, in the conventional inspecting apparatus constructed such that a down stream of air is formed within the apparatus body, the particles are discharged together with the down stream of air to the outside through a bottom region of the apparatus body. In this case, the apparatus is constructed such that members of the apparatus such as the cassette, forks and table occupy most of the horizontal area within the apparatus body. It follows that a smooth down flow of the air stream is prevented by these members, giving rise to turbulence of the air. As a result, the particles are scattered over the entire region of the apparatus body, making it impossible to remove effectively the particles from within the apparatus body. What should also be noted is that the scattered particles are attached again to the object. It follows that it is impossible to solve satisfactorily the problem of the particle attachment to the object.